In almost all electrical and electronic equipment, screw connections are made to wires either directly or using terminal spade lugs that are clamped, soldered or welded to the ends of the wires. These terminal lugs customarily have U-shaped ends, the two tines of which straddle the threaded shank of the screw. In making such a screw connection using a U-shaped terminal lug, the screw is turned until the head of the screw squeezes the tines of the lug onto the body or surface of the connector.
Anyone who has connected the U-shaped terminal spade lugs of a TV antenna twin-lead to the antenna input connector of a TV set knows that these lugs have a strong tendency to rotate with the screw head as they are clamped in place. Also, the clamping and twisting of the screw head tends to splay the tines of the terminal lug, causing them to spread and thus straddle the screw head and fall out. This can be frustrating, time consuming, and expensive to correct, especially in a production facility.
Screw connections are known in which the terminal is shaped in a way somewhat to constrain the terminal lug or wire. One example of such a constraint is illustrated in U.S. Pat No. 3,065,442 granted on Nov. 20, 1962 to H. Hubbell et al. In addition, it is known to make slight projections from the surface of the connector in order to engage terminal lugs and thus to keep them from twisting with the screw head.
Very often, screw connections are located in very close proximity to solder connections. When the terminal is solder coated or well fluxed, the highly-mobile, molten solder has a tendency to flow readily across the terminal surface from the solder connection and into the region of the screw connection. If the solder connection is made prior to the screw connection, the excess solder in the region of the screw connection can provide a substantial solder dross layer between the surface of the connector and the terminal lug, thereby impairing good electrical contact at the screw connection. In addition, the resultant thick coating of solder can cover any projections at the screw terminal and prevent them from biting into the bottom of the terminal lug and can actually lubricate the bottom of the terminal lug to facilitate its rotation with the screw head.
If the solder operation follows the screw connection, the excess solder flowing into the region of the screw connection can also solder that screw connection and frustrate any desired removal of the screw connection.